The use of circuit boards in manufacturing electronic equipment provides many advantages, including minimal size and weight, high reliability, and suitability for automated production. A circuit board comprises an insulating layer carrying conductive metal traces and bonding locations for electrical components. With advances in electronics, particularly in the miniaturization of integrated circuits, a need for multilayer boards has arisen to accommodate the high number of circuit interconnections per unit of surface area on a board.
Multilayer circuit boards utilize separate trace patterns on various layers in three dimensions and layer-to-layer interconnects (i.e., vias or plated throughholes) to implement complex interconnections in a small space. Multilayer circuit boards have been manufactured by laminating separate boards together and by a monolithic, plated-up technique. The higher cost and difficult production processes associated with prior art multilayer circuit boards, however, have limited their utility.
The size and thickness of metal traces determines the magnitude of electrical current that can be safely carried. Thus, it would be desirable to be able to arbitrarily control the size and thickness of conductors within a multilayer structure to carry arbitrary amounts of current.